Your IP : 216.73.217.95


Current Path : /proc/1908984/root/var/tmp/
Upload File :
Current File : //proc/1908984/root/var/tmp/phpNT2EPr

<?php

/**
 * lessphp v0.5.0
 * http://leafo.net/lessphp
 *
 * LESS CSS compiler, adapted from http://lesscss.org
 *
 * Copyright 2013, Leaf Corcoran <leafot@gmail.com>
 * Licensed under MIT or GPLv3, see LICENSE
 */


/**
 * The LESS compiler and parser.
 *
 * Converting LESS to CSS is a three stage process. The incoming file is parsed
 * by `lessc_parser` into a syntax tree, then it is compiled into another tree
 * representing the CSS structure by `lessc`. The CSS tree is fed into a
 * formatter, like `lessc_formatter` which then outputs CSS as a string.
 *
 * During the first compile, all values are *reduced*, which means that their
 * types are brought to the lowest form before being dump as strings. This
 * handles math equations, variable dereferences, and the like.
 *
 * The `parse` function of `lessc` is the entry point.
 *
 * In summary:
 *
 * The `lessc` class creates an instance of the parser, feeds it LESS code,
 * then transforms the resulting tree to a CSS tree. This class also holds the
 * evaluation context, such as all available mixins and variables at any given
 * time.
 *
 * The `lessc_parser` class is only concerned with parsing its input.
 *
 * The `lessc_formatter` takes a CSS tree, and dumps it to a formatted string,
 * handling things like indentation.
 */
class lessc {
    public static $VERSION = "v0.5.0";

    public static $TRUE = array("keyword", "true");
    public static $FALSE = array("keyword", "false");

    protected $libFunctions = array();
    protected $registeredVars = array();
    protected $preserveComments = false;

    public $vPrefix = '@'; // prefix of abstract properties
    public $mPrefix = '$'; // prefix of abstract blocks
    public $parentSelector = '&';

    public $importDisabled = false;
    public $importDir = '';

    protected $numberPrecision = null;

    protected $allParsedFiles = array();

    // set to the parser that generated the current line when compiling
    // so we know how to create error messages
    protected $sourceParser = null;
    protected $sourceLoc = null;

    protected static $nextImportId = 0; // uniquely identify imports

    // attempts to find the path of an import url, returns null for css files
    protected function findImport($url) {
        foreach ((array)$this->importDir as $dir) {
            $full = $dir.(substr($dir, -1) != '/' ? '/' : '').$url;
            if ($this->fileExists($file = $full.'.less') || $this->fileExists($file = $full)) {
                return $file;
            }
        }

        return null;
    }

    protected function fileExists($name) {
        return is_file($name);
    }

    public static function compressList($items, $delim) {
        if (!isset($items[1]) && isset($items[0])) return $items[0];
        else return array('list', $delim, $items);
    }

    public static function preg_quote($what) {
        return preg_quote($what, '/');
    }

    protected function tryImport($importPath, $parentBlock, $out) {
        if ($importPath[0] == "function" && $importPath[1] == "url") {
            $importPath = $this->flattenList($importPath[2]);
        }

        $str = $this->coerceString($importPath);
        if ($str === null) return false;

        $url = $this->compileValue($this->lib_e($str));

        // don't import if it ends in css
        if (substr_compare($url, '.css', -4, 4) === 0) return false;

        $realPath = $this->findImport($url);

        if ($realPath === null) return false;

        if ($this->importDisabled) {
            return array(false, "/* import disabled */");
        }

        if (isset($this->allParsedFiles[realpath($realPath)])) {
            return array(false, null);
        }

        $this->addParsedFile($realPath);
        $parser = $this->makeParser($realPath);
        $root = $parser->parse(file_get_contents($realPath));

        // set the parents of all the block props
        foreach ($root->props as $prop) {
            if ($prop[0] == "block") {
                $prop[1]->parent = $parentBlock;
            }
        }

        // copy mixins into scope, set their parents
        // bring blocks from import into current block
        // TODO: need to mark the source parser these came from this file
        foreach ($root->children as $childName => $child) {
            if (isset($parentBlock->children[$childName])) {
                $parentBlock->children[$childName] = array_merge(
                    $parentBlock->children[$childName],
                    $child);
            } else {
                $parentBlock->children[$childName] = $child;
            }
        }

        $pi = pathinfo($realPath);
        $dir = $pi["dirname"];

        list($top, $bottom) = $this->sortProps($root->props, true);
        $this->compileImportedProps($top, $parentBlock, $out, $parser, $dir);

        return array(true, $bottom, $parser, $dir);
    }

    protected function compileImportedProps($props, $block, $out, $sourceParser, $importDir) {
        $oldSourceParser = $this->sourceParser;

        $oldImport = $this->importDir;

        // TODO: this is because the importDir api is stupid
        $this->importDir = (array)$this->importDir;
        array_unshift($this->importDir, $importDir);

        foreach ($props as $prop) {
            $this->compileProp($prop, $block, $out);
        }

        $this->importDir = $oldImport;
        $this->sourceParser = $oldSourceParser;
    }

    /**
     * Recursively compiles a block.
     *
     * A block is analogous to a CSS block in most cases. A single LESS document
     * is encapsulated in a block when parsed, but it does not have parent tags
     * so all of it's children appear on the root level when compiled.
     *
     * Blocks are made up of props and children.
     *
     * Props are property instructions, array tuples which describe an action
     * to be taken, eg. write a property, set a variable, mixin a block.
     *
     * The children of a block are just all the blocks that are defined within.
     * This is used to look up mixins when performing a mixin.
     *
     * Compiling the block involves pushing a fresh environment on the stack,
     * and iterating through the props, compiling each one.
     *
     * See lessc::compileProp()
     *
     */
    protected function compileBlock($block) {
        switch ($block->type) {
        case "root":
            $this->compileRoot($block);
            break;
        case null:
            $this->compileCSSBlock($block);
            break;
        case "media":
            $this->compileMedia($block);
            break;
        case "directive":
            $name = "@" . $block->name;
            if (!empty($block->value)) {
                $name .= " " . $this->compileValue($this->reduce($block->value));
            }

            $this->compileNestedBlock($block, array($name));
            break;
        default:
            $this->throwError("unknown block type: $block->type\n");
        }
    }

    protected function compileCSSBlock($block) {
        $env = $this->pushEnv();

        $selectors = $this->compileSelectors($block->tags);
        $env->selectors = $this->multiplySelectors($selectors);
        $out = $this->makeOutputBlock(null, $env->selectors);

        $this->scope->children[] = $out;
        $this->compileProps($block, $out);

        $block->scope = $env; // mixins carry scope with them!
        $this->popEnv();
    }

    protected function compileMedia($media) {
        $env = $this->pushEnv($media);
        $parentScope = $this->mediaParent($this->scope);

        $query = $this->compileMediaQuery($this->multiplyMedia($env));

        $this->scope = $this->makeOutputBlock($media->type, array($query));
        $parentScope->children[] = $this->scope;

        $this->compileProps($media, $this->scope);

        if (count($this->scope->lines) > 0) {
            $orphanSelelectors = $this->findClosestSelectors();
            if (!is_null($orphanSelelectors)) {
                $orphan = $this->makeOutputBlock(null, $orphanSelelectors);
                $orphan->lines = $this->scope->lines;
                array_unshift($this->scope->children, $orphan);
                $this->scope->lines = array();
            }
        }

        $this->scope = $this->scope->parent;
        $this->popEnv();
    }

    protected function mediaParent($scope) {
        while (!empty($scope->parent)) {
            if (!empty($scope->type) && $scope->type != "media") {
                break;
            }
            $scope = $scope->parent;
        }

        return $scope;
    }

    protected function compileNestedBlock($block, $selectors) {
        $this->pushEnv($block);
        $this->scope = $this->makeOutputBlock($block->type, $selectors);
        $this->scope->parent->children[] = $this->scope;

        $this->compileProps($block, $this->scope);

        $this->scope = $this->scope->parent;
        $this->popEnv();
    }

    protected function compileRoot($root) {
        $this->pushEnv();
        $this->scope = $this->makeOutputBlock($root->type);
        $this->compileProps($root, $this->scope);
        $this->popEnv();
    }

    protected function compileProps($block, $out) {
        foreach ($this->sortProps($block->props) as $prop) {
            $this->compileProp($prop, $block, $out);
        }
        $out->lines = $this->deduplicate($out->lines);
    }

    /**
     * Deduplicate lines in a block. Comments are not deduplicated. If a
     * duplicate rule is detected, the comments immediately preceding each
     * occurence are consolidated.
     */
    protected function deduplicate($lines) {
        $unique = array();
        $comments = array();

        foreach ($lines as $line) {
            if (strpos($line, '/*') === 0) {
                $comments[] = $line;
                continue;
            }
            if (!in_array($line, $unique)) {
                $unique[] = $line;
            }
            array_splice($unique, array_search($line, $unique), 0, $comments);
            $comments = array();
        }
        return array_merge($unique, $comments);
    }

    protected function sortProps($props, $split = false) {
        $vars = array();
        $imports = array();
        $other = array();
        $stack = array();

        foreach ($props as $prop) {
            switch ($prop[0]) {
            case "comment":
                $stack[] = $prop;
                break;
            case "assign":
                $stack[] = $prop;
                if (isset($prop[1][0]) && $prop[1][0] == $this->vPrefix) {
                    $vars = array_merge($vars, $stack);
                } else {
                    $other = array_merge($other, $stack);
                }
                $stack = array();
                break;
            case "import":
                $id = self::$nextImportId++;
                $prop[] = $id;
                $stack[] = $prop;
                $imports = array_merge($imports, $stack);
                $other[] = array("import_mixin", $id);
                $stack = array();
                break;
            default:
                $stack[] = $prop;
                $other = array_merge($other, $stack);
                $stack = array();
                break;
            }
        }
        $other = array_merge($other, $stack);

        if ($split) {
            return array(array_merge($imports, $vars), $other);
        } else {
            return array_merge($imports, $vars, $other);
        }
    }

    protected function compileMediaQuery($queries) {
        $compiledQueries = array();
        foreach ($queries as $query) {
            $parts = array();
            foreach ($query as $q) {
                switch ($q[0]) {
                case "mediaType":
                    $parts[] = implode(" ", array_slice($q, 1));
                    break;
                case "mediaExp":
                    if (isset($q[2])) {
                        $parts[] = "($q[1]: " .
                            $this->compileValue($this->reduce($q[2])) . ")";
                    } else {
                        $parts[] = "($q[1])";
                    }
                    break;
                case "variable":
                    $parts[] = $this->compileValue($this->reduce($q));
                break;
                }
            }

            if (count($parts) > 0) {
                $compiledQueries[] =  implode(" and ", $parts);
            }
        }

        $out = "@media";
        if (!empty($parts)) {
            $out .= " " .
                implode($this->formatter->selectorSeparator, $compiledQueries);
        }
        return $out;
    }

    protected function multiplyMedia($env, $childQueries = null) {
        if (is_null($env) ||
            !empty($env->block->type) && $env->block->type != "media"
        ) {
            return $childQueries;
        }

        // plain old block, skip
        if (empty($env->block->type)) {
            return $this->multiplyMedia($env->parent, $childQueries);
        }

        $out = array();
        $queries = $env->block->queries;
        if (is_null($childQueries)) {
            $out = $queries;
        } else {
            foreach ($queries as $parent) {
                foreach ($childQueries as $child) {
                    $out[] = array_merge($parent, $child);
                }
            }
        }

        return $this->multiplyMedia($env->parent, $out);
    }

    protected function expandParentSelectors(&$tag, $replace) {
        $parts = explode("$&$", $tag);
        $count = 0;
        foreach ($parts as &$part) {
            $part = str_replace($this->parentSelector, $replace, $part, $c);
            $count += $c;
        }
        $tag = implode($this->parentSelector, $parts);
        return $count;
    }

    protected function findClosestSelectors() {
        $env = $this->env;
        $selectors = null;
        while ($env !== null) {
            if (isset($env->selectors)) {
                $selectors = $env->selectors;
                break;
            }
            $env = $env->parent;
        }

        return $selectors;
    }


    // multiply $selectors against the nearest selectors in env
    protected function multiplySelectors($selectors) {
        // find parent selectors

        $parentSelectors = $this->findClosestSelectors();
        if (is_null($parentSelectors)) {
            // kill parent reference in top level selector
            foreach ($selectors as &$s) {
                $this->expandParentSelectors($s, "");
            }

            return $selectors;
        }

        $out = array();
        foreach ($parentSelectors as $parent) {
            foreach ($selectors as $child) {
                $count = $this->expandParentSelectors($child, $parent);

                // don't prepend the parent tag if & was used
                if ($count > 0) {
                    $out[] = trim($child);
                } else {
                    $out[] = trim($parent . ' ' . $child);
                }
            }
        }

        return $out;
    }

    // reduces selector expressions
    protected function compileSelectors($selectors) {
        $out = array();

        foreach ($selectors as $s) {
            if (is_array($s)) {
                list(, $value) = $s;
                $out[] = trim($this->compileValue($this->reduce($value)));
            } else {
                $out[] = $s;
            }
        }

        return $out;
    }

    protected function eq($left, $right) {
        return $left == $right;
    }

    protected function patternMatch($block, $orderedArgs, $keywordArgs) {
        // match the guards if it has them
        // any one of the groups must have all its guards pass for a match
        if (!empty($block->guards)) {
            $groupPassed = false;
            foreach ($block->guards as $guardGroup) {
                foreach ($guardGroup as $guard) {
                    $this->pushEnv();
                    $this->zipSetArgs($block->args, $orderedArgs, $keywordArgs);

                    $negate = false;
                    if ($guard[0] == "negate") {
                        $guard = $guard[1];
                        $negate = true;
                    }

                    $passed = $this->reduce($guard) == self::$TRUE;
                    if ($negate) $passed = !$passed;

                    $this->popEnv();

                    if ($passed) {
                        $groupPassed = true;
                    } else {
                        $groupPassed = false;
                        break;
                    }
                }

                if ($groupPassed) break;
            }

            if (!$groupPassed) {
                return false;
            }
        }

        if (empty($block->args)) {
            return $block->isVararg || empty($orderedArgs) && empty($keywordArgs);
        }

        $remainingArgs = $block->args;
        if ($keywordArgs) {
            $remainingArgs = array();
            foreach ($block->args as $arg) {
                if ($arg[0] == "arg" && isset($keywordArgs[$arg[1]])) {
                    continue;
                }

                $remainingArgs[] = $arg;
            }
        }

        $i = -1; // no args
        // try to match by arity or by argument literal
        foreach ($remainingArgs as $i => $arg) {
            switch ($arg[0]) {
            case "lit":
                if (empty($orderedArgs[$i]) || !$this->eq($arg[1], $orderedArgs[$i])) {
                    return false;
                }
                break;
            case "arg":
                // no arg and no default value
                if (!isset($orderedArgs[$i]) && !isset($arg[2])) {
                    return false;
                }
                break;
            case "rest":
                $i--; // rest can be empty
                break 2;
            }
        }

        if ($block->isVararg) {
            return true; // not having enough is handled above
        } else {
            $numMatched = $i + 1;
            // greater than because default values always match
            return $numMatched >= count($orderedArgs);
        }
    }

    protected function patternMatchAll($blocks, $orderedArgs, $keywordArgs, $skip = array()) {
        $matches = null;
        foreach ($blocks as $block) {
            // skip seen blocks that don't have arguments
            if (isset($skip[$block->id]) && !isset($block->args)) {
                continue;
            }

            if ($this->patternMatch($block, $orderedArgs, $keywordArgs)) {
                $matches[] = $block;
            }
        }

        return $matches;
    }

    // attempt to find blocks matched by path and args
    protected function findBlocks($searchIn, $path, $orderedArgs, $keywordArgs, $seen = array()) {
        if ($searchIn == null) return null;
        if (isset($seen[$searchIn->id])) return null;
        $seen[$searchIn->id] = true;

        $name = $path[0];

        if (isset($searchIn->children[$name])) {
            $blocks = $searchIn->children[$name];
            if (count($path) == 1) {
                $matches = $this->patternMatchAll($blocks, $orderedArgs, $keywordArgs, $seen);
                if (!empty($matches)) {
                    // This will return all blocks that match in the closest
                    // scope that has any matching block, like lessjs
                    return $matches;
                }
            } else {
                $matches = array();
                foreach ($blocks as $subBlock) {
                    $subMatches = $this->findBlocks($subBlock,
                        array_slice($path, 1), $orderedArgs, $keywordArgs, $seen);

                    if (!is_null($subMatches)) {
                        foreach ($subMatches as $sm) {
                            $matches[] = $sm;
                        }
                    }
                }

                return count($matches) > 0 ? $matches : null;
            }
        }
        if ($searchIn->parent === $searchIn) return null;
        return $this->findBlocks($searchIn->parent, $path, $orderedArgs, $keywordArgs, $seen);
    }

    // sets all argument names in $args to either the default value
    // or the one passed in through $values
    protected function zipSetArgs($args, $orderedValues, $keywordValues) {
        $assignedValues = array();

        $i = 0;
        foreach ($args as $a) {
            if ($a[0] == "arg") {
                if (isset($keywordValues[$a[1]])) {
                    // has keyword arg
                    $value = $keywordValues[$a[1]];
                } elseif (isset($orderedValues[$i])) {
                    // has ordered arg
                    $value = $orderedValues[$i];
                    $i++;
                } elseif (isset($a[2])) {
                    // has default value
                    $value = $a[2];
                } else {
                    $this->throwError("Failed to assign arg " . $a[1]);
                    $value = null; // :(
                }

                $value = $this->reduce($value);
                $this->set($a[1], $value);
                $assignedValues[] = $value;
            } else {
                // a lit
                $i++;
            }
        }

        // check for a rest
        $last = end($args);
        if ($last[0] == "rest") {
            $rest = array_slice($orderedValues, count($args) - 1);
            $this->set($last[1], $this->reduce(array("list", " ", $rest)));
        }

        // wow is this the only true use of PHP's + operator for arrays?
        $this->env->arguments = $assignedValues + $orderedValues;
    }

    // compile a prop and update $lines or $blocks appropriately
    protected function compileProp($prop, $block, $out) {
        // set error position context
        $this->sourceLoc = isset($prop[-1]) ? $prop[-1] : -1;

        switch ($prop[0]) {
        case 'assign':
            list(, $name, $value) = $prop;
            if ($name[0] == $this->vPrefix) {
                $this->set($name, $value);
            } else {
                $out->lines[] = $this->formatter->property($name,
                        $this->compileValue($this->reduce($value)));
            }
            break;
        case 'block':
            list(, $child) = $prop;
            $this->compileBlock($child);
            break;
        case 'mixin':
            list(, $path, $args, $suffix) = $prop;

            $orderedArgs = array();
            $keywordArgs = array();
            foreach ((array)$args as $arg) {
                $argval = null;
                switch ($arg[0]) {
                case "arg":
                    if (!isset($arg[2])) {
                        $orderedArgs[] = $this->reduce(array("variable", $arg[1]));
                    } else {
                        $keywordArgs[$arg[1]] = $this->reduce($arg[2]);
                    }
                    break;

                case "lit":
                    $orderedArgs[] = $this->reduce($arg[1]);
                    break;
                default:
                    $this->throwError("Unknown arg type: " . $arg[0]);
                }
            }

            $mixins = $this->findBlocks($block, $path, $orderedArgs, $keywordArgs);

            if ($mixins === null) {
                $this->throwError("{$prop[1][0]} is undefined");
            }

            foreach ($mixins as $mixin) {
                if ($mixin === $block && !$orderedArgs) {
                    continue;
                }

                $haveScope = false;
                if (isset($mixin->parent->scope)) {
                    $haveScope = true;
                    $mixinParentEnv = $this->pushEnv();
                    $mixinParentEnv->storeParent = $mixin->parent->scope;
                }

                $haveArgs = false;
                if (isset($mixin->args)) {
                    $haveArgs = true;
                    $this->pushEnv();
                    $this->zipSetArgs($mixin->args, $orderedArgs, $keywordArgs);
                }

                $oldParent = $mixin->parent;
                if ($mixin != $block) $mixin->parent = $block;

                foreach ($this->sortProps($mixin->props) as $subProp) {
                    if ($suffix !== null &&
                        $subProp[0] == "assign" &&
                        is_string($subProp[1]) &&
                        $subProp[1][0] != $this->vPrefix
                    ) {
                        $subProp[2] = array(
                            'list', ' ',
                            array($subProp[2], array('keyword', $suffix))
                        );
                    }

                    $this->compileProp($subProp, $mixin, $out);
                }

                $mixin->parent = $oldParent;

                if ($haveArgs) $this->popEnv();
                if ($haveScope) $this->popEnv();
            }

            break;
        case 'raw':
            $out->lines[] = $prop[1];
            break;
        case "directive":
            list(, $name, $value) = $prop;
            $out->lines[] = "@$name " . $this->compileValue($this->reduce($value)).';';
            break;
        case "comment":
            $out->lines[] = $prop[1];
            break;
        case "import":
            list(, $importPath, $importId) = $prop;
            $importPath = $this->reduce($importPath);

            if (!isset($this->env->imports)) {
                $this->env->imports = array();
            }

            $result = $this->tryImport($importPath, $block, $out);

            $this->env->imports[$importId] = $result === false ?
                array(false, "@import " . $this->compileValue($importPath).";") :
                $result;

            break;
        case "import_mixin":
            list(,$importId) = $prop;
            $import = $this->env->imports[$importId];
            if ($import[0] === false) {
                if (isset($import[1])) {
                    $out->lines[] = $import[1];
                }
            } else {
                list(, $bottom, $parser, $importDir) = $import;
                $this->compileImportedProps($bottom, $block, $out, $parser, $importDir);
            }

            break;
        default:
            $this->throwError("unknown op: {$prop[0]}\n");
        }
    }


    /**
     * Compiles a primitive value into a CSS property value.
     *
     * Values in lessphp are typed by being wrapped in arrays, their format is
     * typically:
     *
     *     array(type, contents [, additional_contents]*)
     *
     * The input is expected to be reduced. This function will not work on
     * things like expressions and variables.
     */
    public function compileValue($value) {
        switch ($value[0]) {
        case 'list':
            // [1] - delimiter
            // [2] - array of values
            return implode($value[1], array_map(array($this, 'compileValue'), $value[2]));
        case 'raw_color':
            if (!empty($this->formatter->compressColors)) {
                return $this->compileValue($this->coerceColor($value));
            }
            return $value[1];
        case 'keyword':
            // [1] - the keyword
            return $value[1];
        case 'number':
            list(, $num, $unit) = $value;
            // [1] - the number
            // [2] - the unit
            if ($this->numberPrecision !== null) {
                $num = round($num, $this->numberPrecision);
            }
            return $num . $unit;
        case 'string':
            // [1] - contents of string (includes quotes)
            list(, $delim, $content) = $value;
            foreach ($content as &$part) {
                if (is_array($part)) {
                    $part = $this->compileValue($part);
                }
            }
            return $delim . implode($content) . $delim;
        case 'color':
            // [1] - red component (either number or a %)
            // [2] - green component
            // [3] - blue component
            // [4] - optional alpha component
            list(, $r, $g, $b) = $value;
            $r = round($r);
            $g = round($g);
            $b = round($b);

            if (count($value) == 5 && $value[4] != 1) { // rgba
                return 'rgba('.$r.','.$g.','.$b.','.$value[4].')';
            }

            $h = sprintf("#%02x%02x%02x", $r, $g, $b);

            if (!empty($this->formatter->compressColors)) {
                // Converting hex color to short notation (e.g. #003399 to #039)
                if ($h[1] === $h[2] && $h[3] === $h[4] && $h[5] === $h[6]) {
                    $h = '#' . $h[1] . $h[3] . $h[5];
                }
            }

            return $h;

        case 'function':
            list(, $name, $args) = $value;
            return $name.'('.$this->compileValue($args).')';
        default: // assumed to be unit
            $this->throwError("unknown value type: $value[0]");
        }
    }

    protected function lib_pow($args) {
        list($base, $exp) = $this->assertArgs($args, 2, "pow");
        return pow($this->assertNumber($base), $this->assertNumber($exp));
    }

    protected function lib_pi() {
        return pi();
    }

    protected function lib_mod($args) {
        list($a, $b) = $this->assertArgs($args, 2, "mod");
        return $this->assertNumber($a) % $this->assertNumber($b);
    }

    protected function lib_tan($num) {
        return tan($this->assertNumber($num));
    }

    protected function lib_sin($num) {
        return sin($this->assertNumber($num));
    }

    protected function lib_cos($num) {
        return cos($this->assertNumber($num));
    }

    protected function lib_atan($num) {
        $num = atan($this->assertNumber($num));
        return array("number", $num, "rad");
    }

    protected function lib_asin($num) {
        $num = asin($this->assertNumber($num));
        return array("number", $num, "rad");
    }

    protected function lib_acos($num) {
        $num = acos($this->assertNumber($num));
        return array("number", $num, "rad");
    }

    protected function lib_sqrt($num) {
        return sqrt($this->assertNumber($num));
    }

    protected function lib_extract($value) {
        list($list, $idx) = $this->assertArgs($value, 2, "extract");
        $idx = $this->assertNumber($idx);
        // 1 indexed
        if ($list[0] == "list" && isset($list[2][$idx - 1])) {
            return $list[2][$idx - 1];
        }
    }

    protected function lib_isnumber($value) {
        return $this->toBool($value[0] == "number");
    }

    protected function lib_isstring($value) {
        return $this->toBool($value[0] == "string");
    }

    protected function lib_iscolor($value) {
        return $this->toBool($this->coerceColor($value));
    }

    protected function lib_iskeyword($value) {
        return $this->toBool($value[0] == "keyword");
    }

    protected function lib_ispixel($value) {
        return $this->toBool($value[0] == "number" && $value[2] == "px");
    }

    protected function lib_ispercentage($value) {
        return $this->toBool($value[0] == "number" && $value[2] == "%");
    }

    protected function lib_isem($value) {
        return $this->toBool($value[0] == "number" && $value[2] == "em");
    }

    protected function lib_isrem($value) {
        return $this->toBool($value[0] == "number" && $value[2] == "rem");
    }

    protected function lib_rgbahex($color) {
        $color = $this->coerceColor($color);
        if (is_null($color)) {
            $this->throwError("color expected for rgbahex");
        }

        return sprintf("#%02x%02x%02x%02x",
            isset($color[4]) ? $color[4] * 255 : 255,
            $color[1],
            $color[2],
            $color[3]
        );
    }

    protected function lib_argb($color){
        return $this->lib_rgbahex($color);
    }

    /**
     * Given an url, decide whether to output a regular link or the base64-encoded contents of the file
     *
     * @param  array  $value either an argument list (two strings) or a single string
     * @return string        formatted url(), either as a link or base64-encoded
     */
    protected function lib_data_uri($value) {
        $mime = ($value[0] === 'list') ? $value[2][0][2] : null;
        $url = ($value[0] === 'list') ? $value[2][1][2][0] : $value[2][0];

        $fullpath = $this->findImport($url);

        if ($fullpath && ($fsize = filesize($fullpath)) !== false) {
            // IE8 can't handle data uris larger than 32KB
            if ($fsize/1024 < 32) {
                if (is_null($mime)) {
                    if (class_exists('finfo')) { // php 5.3+
                        $finfo = new finfo(FILEINFO_MIME);
                        $mime = explode('; ', $finfo->file($fullpath));
                        $mime = $mime[0];
                    } elseif (function_exists('mime_content_type')) { // PHP 5.2
                        $mime = mime_content_type($fullpath);
                    }
                }

                if (!is_null($mime)) // fallback if the mime type is still unknown
                    $url = sprintf('data:%s;base64,%s', $mime, base64_encode(file_get_contents($fullpath)));
            }
        }

        return 'url("'.$url.'")';
    }

    // utility func to unquote a string
    protected function lib_e($arg) {
        switch ($arg[0]) {
            case "list":
                $items = $arg[2];
                if (isset($items[0])) {
                    return $this->lib_e($items[0]);
                }
                $this->throwError("unrecognised input");
            case "string":
                $arg[1] = "";
                return $arg;
            case "keyword":
                return $arg;
            default:
                return array("keyword", $this->compileValue($arg));
        }
    }

    protected function lib__sprintf($args) {
        if ($args[0] != "list") return $args;
        $values = $args[2];
        $string = array_shift($values);
        $template = $this->compileValue($this->lib_e($string));

        $i = 0;
        if (preg_match_all('/%[dsa]/', $template, $m)) {
            foreach ($m[0] as $match) {
                $val = isset($values[$i]) ?
                    $this->reduce($values[$i]) : array('keyword', '');

                // lessjs compat, renders fully expanded color, not raw color
                if ($color = $this->coerceColor($val)) {
                    $val = $color;
                }

                $i++;
                $rep = $this->compileValue($this->lib_e($val));
                $template = preg_replace('/'.self::preg_quote($match).'/',
                    $rep, $template, 1);
            }
        }

        $d = $string[0] == "string" ? $string[1] : '"';
        return array("string", $d, array($template));
    }

    protected function lib_floor($arg) {
        $value = $this->assertNumber($arg);
        return array("number", floor($value), $arg[2]);
    }

    protected function lib_ceil($arg) {
        $value = $this->assertNumber($arg);
        return array("number", ceil($value), $arg[2]);
    }

    protected function lib_round($arg) {
        if ($arg[0] != "list") {
            $value = $this->assertNumber($arg);
            return array("number", round($value), $arg[2]);
        } else {
            $value = $this->assertNumber($arg[2][0]);
            $precision = $this->assertNumber($arg[2][1]);
            return array("number", round($value, $precision), $arg[2][0][2]);
        }
    }

    protected function lib_unit($arg) {
        if ($arg[0] == "list") {
            list($number, $newUnit) = $arg[2];
            return array("number", $this->assertNumber($number),
                $this->compileValue($this->lib_e($newUnit)));
        } else {
            return array("number", $this->assertNumber($arg), "");
        }
    }

    /**
     * Helper function to get arguments for color manipulation functions.
     * takes a list that contains a color like thing and a percentage
     */
    public function colorArgs($args) {
        if ($args[0] != 'list' || count($args[2]) < 2) {
            return array(array('color', 0, 0, 0), 0);
        }
        list($color, $delta) = $args[2];
        $color = $this->assertColor($color);
        $delta = floatval($delta[1]);

        return array($color, $delta);
    }

    protected function lib_darken($args) {
        list($color, $delta) = $this->colorArgs($args);

        $hsl = $this->toHSL($color);
        $hsl[3] = $this->clamp($hsl[3] - $delta, 100);
        return $this->toRGB($hsl);
    }

    protected function lib_lighten($args) {
        list($color, $delta) = $this->colorArgs($args);

        $hsl = $this->toHSL($color);
        $hsl[3] = $this->clamp($hsl[3] + $delta, 100);
        return $this->toRGB($hsl);
    }

    protected function lib_saturate($args) {
        list($color, $delta) = $this->colorArgs($args);

        $hsl = $this->toHSL($color);
        $hsl[2] = $this->clamp($hsl[2] + $delta, 100);
        return $this->toRGB($hsl);
    }

    protected function lib_desaturate($args) {
        list($color, $delta) = $this->colorArgs($args);

        $hsl = $this->toHSL($color);
        $hsl[2] = $this->clamp($hsl[2] - $delta, 100);
        return $this->toRGB($hsl);
    }

    protected function lib_spin($args) {
        list($color, $delta) = $this->colorArgs($args);

        $hsl = $this->toHSL($color);

        $hsl[1] = $hsl[1] + $delta % 360;
        if ($hsl[1] < 0) {
            $hsl[1] += 360;
        }

        return $this->toRGB($hsl);
    }

    protected function lib_fadeout($args) {
        list($color, $delta) = $this->colorArgs($args);
        $color[4] = $this->clamp((isset($color[4]) ? $color[4] : 1) - $delta/100);
        return $color;
    }

    protected function lib_fadein($args) {
        list($color, $delta) = $this->colorArgs($args);
        $color[4] = $this->clamp((isset($color[4]) ? $color[4] : 1) + $delta/100);
        return $color;
    }

    protected function lib_hue($color) {
        $hsl = $this->toHSL($this->assertColor($color));
        return round($hsl[1]);
    }

    protected function lib_saturation($color) {
        $hsl = $this->toHSL($this->assertColor($color));
        return round($hsl[2]);
    }

    protected function lib_lightness($color) {
        $hsl = $this->toHSL($this->assertColor($color));
        return round($hsl[3]);
    }

    // get the alpha of a color
    // defaults to 1 for non-colors or colors without an alpha
    protected function lib_alpha($value) {
        if (!is_null($color = $this->coerceColor($value))) {
            return isset($color[4]) ? $color[4] : 1;
        }
    }

    // set the alpha of the color
    protected function lib_fade($args) {
        list($color, $alpha) = $this->colorArgs($args);
        $color[4] = $this->clamp($alpha / 100.0);
        return $color;
    }

    protected function lib_percentage($arg) {
        $num = $this->assertNumber($arg);
        return array("number", $num*100, "%");
    }

    /**
     * Mix color with white in variable proportion.
     *
     * It is the same as calling `mix(#ffffff, @color, @weight)`.
     *
     *     tint(@color, [@weight: 50%]);
     *
     * http://lesscss.org/functions/#color-operations-tint
     *
     * @return array Color
     */
    protected function lib_tint($args) {
        $white = array('color', 255, 255, 255);
        if ($args[0] == 'color') {
            return $this->lib_mix(array( 'list', ',', array($white, $args) ));
        } elseif ($args[0] == "list" && count($args[2]) == 2) {
            return $this->lib_mix(array( $args[0], $args[1], array($white, $args[2][0], $args[2][1]) ));
        } else {
            $this->throwError("tint expects (color, weight)");
        }
    }

    /**
     * Mix color with black in variable proportion.
     *
     * It is the same as calling `mix(#000000, @color, @weight)`
     *
     *     shade(@color, [@weight: 50%]);
     *
     * http://lesscss.org/functions/#color-operations-shade
     *
     * @return array Color
     */
    protected function lib_shade($args) {
        $black = array('color', 0, 0, 0);
        if ($args[0] == 'color') {
            return $this->lib_mix(array( 'list', ',', array($black, $args) ));
        } elseif ($args[0] == "list" && count($args[2]) == 2) {
            return $this->lib_mix(array( $args[0], $args[1], array($black, $args[2][0], $args[2][1]) ));
        } else {
            $this->throwError("shade expects (color, weight)");
        }
    }

    // mixes two colors by weight
    // mix(@color1, @color2, [@weight: 50%]);
    // http://sass-lang.com/docs/yardoc/Sass/Script/Functions.html#mix-instance_method
    protected function lib_mix($args) {
        if ($args[0